1. Field of the Invention
The present invention relates to a semiconductor device and a method of manufacturing the semiconductor device, and more particularly to the passivation of the periphery of a bonding pad.
2. Description of the Related Art
When a semiconductor device such as a VLSI (very large scale integration) is to be manufactured, a passivation structure is very important around a bonding pad and a bump formed on an electrode pad, and various endeavors have been made to enhance a productivity while maintaining a reliability.
In recent years, a structure using a polyimide resin for a passivation film has variously been proposed. By way of example, as shown in FIG. 21, there are formed an electrode pad 2 comprising an aluminum layer formed to come in contact with a surface of a semiconductor substrate 1 or a wiring layer provided on the surface of the semiconductor substrate, and a bonding pad 5 formed of metal in a contact hole H provided on a silicon nitride film 3 for covering the upper layer of the electrode pad 2 through a TiW layer to be an intermediate layer 4. A polyimide resin film 7 to be a passivation film is formed around the metallic bonding pad 5.
Such a structure is formed through the following manufacturing process.
First of all, a wiring layer (not shown) and an interlayer insulating film (not shown) are formed on the surface of the silicon substrate 1 provided with an element region and a through hole (not shown) is formed by photolithography. Then, the aluminum layer is evaporated and the wiring (not shown) and the electrode pad 2 are subjected to patterning by photolithography. Thereafter, the silicon nitride film 3 is formed on the upper layer of the electrode pad 2 and is subjected to patterning by the photolithography, and a contact hole is formed in the central part of the electrode pad 2 to cover the peripheral edge of the electrode pad 2 with a silicon nitride film (FIG. 22).
As shown in FIG. 23, subsequently, the polyimide resin film 7 to be a passivation film is formed and is subjected to patterning, thereby exposing the electrode pad 2 as shown in FIG. 24.
If the aluminum layer is exposed to a surface, it is apt to be corroded. As shown in FIG. 25, therefore, a titanium tungsten TiW film to be a barrier layer is formed as the intermediate layer 4 on the aluminum layer by the sputtering method and the metal layer 5 to be a bonding pad is then formed.
As shown in FIG. 26, thereafter, the metal layer 5 and the intermediate layer 4 are subjected to patterning by the photolithography.
Accordingly, it is desirable that the edge of the pad layer 5 is coincident with that of the polyimide resin film 7. In consideration of mask precision, there is a problem in that the edges are coincident with difficulty. On the other hand, there is a problem in that a short circuit is apt to be caused if the metal layer 5 and the intermediate layer 4 get over the passivation film 7. For this reason, the patterning is carried out in consideration of precision in the photolithography.
Consequently, a clearance is generated between the polyimide resin film constituting the passivation film and the pad layer 5 so that TiW which is easily oxidized is exposed. For this reason, there is a problem in that corrosion is apt to be caused, the passivation effect cannot be obtained well and the reliability is thereby deteriorated.
[Problems that the Invention Is to Solve]
In the conventional pad structure, thus, there is a problem in that a water content enters from the clearance between the passivation film and the bonding pad layer, the electrode pad such as aluminum is easily corroded and the reliability is thereby maintained with difficulty.